Optical couplers join one or more input optical fibers to one or more output optical fibers. They allow light being carried by an input fiber(s) to be transferred to, split between, or merged into an output optical fiber(s). They play an important role in fiber telecommunications, cable television links, and data communications.
At present, couplers are made by fusing optical fibers or by attaching fibers to a planar, glass integrated optical device which guides the light from the input fiber(s) to output fiber(s) attached at the opposite end of the device. Both of these methods are quite labor intensive and quite costly. The cost is also proportionate to the number of output fibers desired (because of the cost in carefully fusing or attaching each individual fiber). These labor-intensive processes also prohibit these devices from being mass produced.
Unlike optical couplers, channel waveguides are widely used and easily produced. In the past twenty years, numerous methods for producing these waveguides have been developed. For instance, electroplating nickel onto a master to form a channel waveguide mold and the use of photo-resist techniques to form waveguide channels have been known for a number of years. More recently, photolithographic techniques have been used to make improved waveguides. Cast-and-cure methods have also supplemented the older injection molding methods of forming polymeric channel waveguides. None of these techniques teach a means for passively aligning optical fibers to such channel waveguides, however.
In a recent publication (A. Neyer, T. Knoche, and L. Muller, Electronics Letters, 29, 399 (1993)), a method of cheaply reproducing numerous waveguides was disclosed. This method involved creating a master mold (for straight waveguide channels only) in photo-resist followed by electroplating in nickel, forming waveguide grooves in poly(methyl methacrylate) by injection molding, filling the grooves with a UV-cured resin having a high index of refraction, placing a flat top piece on the resin-substrate article, and curing the whole. In this publication, the authors suggested that this process could be used to simultaneously manufacture optical waveguide structures and fiber alignment grooves in one fabrication step. How this process could be modified to include such fiber groove formation and alignment was not mentioned or suggested.